Deserts/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A boy, Tim, is lying on his back on sand. TIM: Water. Water. A robot, Moby, is lying on his back next to Tim. Both of them have beards. MOBY: Beep. Beep. TIM: Muh?! The scene spins away to Tim, with no beard, wearing a towel on his head. Tim and Moby appear under a tree in a desert. Moby is waving a letter at Tim. Tim reads from the typed letter. TIM: Dear Tim and Moby, What makes a desert so hot? From, Wei-Ling. MOBY: Beep. TIM: Actually, deserts don't have to be hot, like this one, just very dry. There are hot deserts, cold deserts, and sort of in-between deserts, too. Images show the deserts Tim describes. TIM: Deserts are also known as arid regions, and they're the driest places on Earth. A world map shows arid regions. TIM: Because moisture prevents soil erosion, arid regions are usually pretty rocky. Some are covered in huge hills of sand called dunes, which are shaped and pushed around by the wind. Side by side images show a rocky and a sandy dunes arid region. MOBY: Beep. TIM: Well, a desert's climate is mainly a factor of where it is on the planet. Hot deserts, like the Sahara in Africa, are found in two belts, around thirty degrees north and south of the equator. The equator and thirty degrees north and south of it are shown on the world map of arid regions. TIM: Permanent areas of high pressure in these latitudes keep dry air circulating near the planet's surface. An animation shows the two belts where hot deserts occur on a globe. Arrows show the conditions that produce high pressure in the belts. TIM: And the Sun's rays hit the earth pretty directly here. An animation shows arrows pointing to where the sun hits the globe. TIM: All that hot, dry air means lots of evaporation. An image shows a body of water evaporating in a desert. TIM: With so little water to cool the land and air, temperatures in hot deserts can reach over fifty-five degrees Celsius, or more than one hundred thirty degrees Fahrenheit. MOBY: Beep. TIM: Well, we could wait. Deserts cool off fast once the sun goes down. MOBY: Beep. Moby presses a transporter button in his wrist. Tim and Moby transport to a cold desert. A penguin exchanges looks with Tim and Moby. TIM: Whoa. High-pressure systems and cold ocean currents near the earth's poles are responsible for the polar deserts. A global map shows the highlighted polar deserts to the north and south. TIM: This is the Antarctic desert, and it's the biggest in the world. The penguin holds its wings up, make sounds, and bows to Moby. A group of penguins are behind him. MOBY: Beep. TIM: Well, the colder the air, the less moisture it can hold. And Antarctica has the lowest temperatures on record. An image shows a person holding a thermometer near a trailer equipped with a satellite dish. The thermometer reads minus eighty-nine degrees Celsius. TIM: Most organisms in polar deserts live near the coasts, where the oceans provide food and temperatures are a bit warmer. A group of penguins hold their wings up while making sounds and bow at Moby. Moby presses the transporter button in his wrist. Tim and Moby are transported to another desert. TIM: Local geography has a big impact on arid regions, too. Asia's Gobi Desert formed because it's so far away from the ocean. The global map shows Tim and Moby at the Gobi Desert in Asia. TIM: By the time any clouds arrive from the coast, they've most likely already dumped all their rain. An animation shows moving clouds. TIM: But hot or cold, deserts are some of the harshest environments on the planet. It takes special types of plants and animals to survive in them. In hot deserts, most animals sleep below ground or in patches of shade during the day. An animation shows sleeping animals in holes below ground on a sunny day. Eyes peer out of a shady spot in a plant. TIM: They come out a night when it's cooler. An animation shows a scorpion walking at night. TIM: Animals in cold deserts have the opposite problem. They need thick fur and layers of fat to weather the cold temperatures. An image shows a polar bear, a seal, and a yak. TIM: Many desert organisms also need special adaptations to get and keep the water they need. Cactuses use sprawling, shallow roots to soak up water. They can store lots of water in their rubbery stems, and they don't have any leaves to lose moisture through. An image shows a cactus and its roots. Arrows point to its roots and stem. TIM: I bet you can guess what the spines are for. An image shows the cactus's spines. An animation shows a buzzing salamander picturing the cactus as a glass of a cold drink. The salamander tries to bite the cactus, gets the plant's spines in its face, and cries tears. TIM: Penguins and seals are able to drink seawater. An animation shows a swimming penguin taking a gulp of water. TIM: And many desert mammals have evolved special ways to keep water. Kangaroo rats, for instance, live in underground dens which stay cool and keeps the little guys from sweating out too much water. The rats also use the enclosed space to recycle the water they release as they breathe. An image shows a kangaroo rat in an underground den. TIM: Even humans have managed to carve out a living in every desert in the world, except Antarctica. Side by side images show a person dressed warmly in a cold desert and a man covered in loose clothing in a hot desert. TIM: Do you think you could survive in a cold desert? MOBY: Beep. Moby holds up an ice-cream pop. TIM: No, I said cold desert. Desert. That's ice cream. Category:BrainPOP Transcripts